Antigen-specific B cells will be purified by rosetting-techniques. The surface events that accompany interaction of such cells with specific immunogen or tolerogen will then be examined by both biochemical and immunofluorescent techniques. Of particular interest will be the aggregation and pinocytosis of IgM-and IgD-receptors and their regeneration. The role of other surface receptors in tolerance induction will also be investigated by blocking those receptors with specific antibody before induction of tolerance. Alterations in the morphology of tolerized cells will be studied by phase contrast microscopy and electron microscopy of such purified populations after interaction with tolerogen. The fate of tolerogen will be determined by subcellular fractionation experiments in order to determine the intracellular sites of tolerogen accumulation and to search for biological correlates of this distribution.